After the most important considerations of cut and style, you'll see the functional difference between Light, Medium and Heavy armours if you look at the Protection percentage. Light armour can protect you from up to about 10% of physical damage, medium armour about 25% and heavy armour about 50%. Medium and Heavy armours also give a boost, for each piece, to your HP, which is related to the quality level of the armour.
If you want to melee then look for medium or heavy armour, though player made pieces may well be in short supply on the starter isles, and look for high Protection percentage. Physical damage comes in three types - Slash, Blunt and Pierce - and below the Protection percentage you'll find "Max vs" stats corresponding to these different types. This is the maximum amount of damage the armour will absorb per blow of this type. I think the most important thing to know about these is that predators always slash or pierce, so you may be best advised to look for high values there. I think ragus and gingo always slash, goari pierce. Heavy armour tends to come with a negative dodge modifier so you're probably best to set yourself to parry and see if you can find armour that helps you to do this.
If you mean to burn your attacker or prey with acid or cold, then you'll probably find light armour most suitable because it won't add to the Sap or HP costs of your spells. In this case you're not concerned about the Protection percentage because you'd be much better off not getting hit in the first place - see if you can find clothes with a positive Dodge modifier and make sure you are set to dodge and not parry
. Medium armour can work well for magic too if you don't have someone to keep the dogs from you.
